Fusible apparatus for protecting automactic sprinklers



July 23, 1968 RTM. HODNETT FUSIBLE APPARATUS FOR PROTECTING AUTOMATIC SPRINKLERS /Idu T n m m0 H v N M m m R Fae Filed Feb. 24, 1966 BY; r

TT ORNEY United States Patent 3,393,746 FUSIBLE APPARATUS FOR PROTECTING AUTOMACTIC SPRINKLERS Robert M. Hodnett, Providence, R.I., assignor to Grinnell Corporation, Providence, R.I., a corporation of Delaware Fiied Feb. 24, 1966, Ser. No. 529,731 1 Claim. (Cl. 169-41) ABSTRACT OF THE DISCLOSURE For a fire protection sprinkler head which projects downwardly partially through a ceiling opening and for a ceiling plate which is adjustably mounted on such sprinkler head and has a flange overlying the ceiling surface around the opening, a solder cap enclosing the projecting part of the head, covering the opening and having a flange covering the plate flange, such cap flange being secured to the plate flange by solder rivets which are integral with the back side of the cap flange, and such cap flange having a smooth front surface opposite said rivets, whereby in the region of the sprinkler head the surfaces presented into the room are only the cap surfaces which can be easily cleaned by wiping.

BACKGROUND OF THE INVENTION Field of the invention In recent years, as a result of increased requirements for exacting precision, the assembling of complex componcnts, such as are used in the space program and pharmaceutical houses, has been carried out in superclean and sterile rooms, often referred to as clean rooms.

To maintain a superclean atmosphere requires frequent, periodic sterilization by wiping all of the surfaces in the room. Normal pendent and recessed pendent fire protection sprinklers have so many irregular and varied surfaces and crevices that to clean the number of heads required in a room is so onerous a job that in the past no sprinklers have been installed in most of the rooms. This naturally lessens the available protection for a very valuable installation.

Description of the prior art To solve certain problems arising from the use of sprinklers in undesirbale locations, such as in corrosive atmospheres, several attempts have been made in the past to place protective covers over the sprinklers. These protective devices, here called prior art devices, have sought to solve problems quite different from those overcome by the present invention. However, because of their outward apparent similarity to the present invention it is considered desirable to briefly discuss them. These prior art devices have generally fallen into two categories: those made of flammable plastic and those of a more permanent material, such as glass. Neither type, however, has proven suitable for use in rooms where cleanliness is a prime concern.

An example of a flammable plastic corrosion protector is disclosed in US. Patent No. 2,890,758 to Pfalzgraff et al. This patent describes the problem encountered in the use of a cap made of a permanent material such as a jointed glass cover, namely the possible removal during a fire of only part of the cap which would leave a portion of the cap to destroy the desirable spray pattern.

With caps made of a single piece of glass or a single piece of durable metal, a joint between the cap and head that is capable of fusing due to a rise in temperature, is normally required to permit release of the cap ice when a fire occurs. A disadvantage of using such a cap in the environment of a room where cleanliness is important arises when it must be replaced due to the loosening of the cap either because it has been knocked loose by someones wiping or because the cap has been released due to a fire. In replacing a prior art cap a maintenance man might fasten it in place by a permanent fastening such as a screw or a nut and bolt combination instead of restoring the fusible joint. This, of course, would prevent the proper performance of such a cap when the necessity arose for having its enclosed sprinkler operate. The present invention, on the other hand, is operable even if the fusible cap is permanently fastened to the remainder of the combination. However, the cap replacement procedure is so simple that it is unlikely that a maintenance man would attempt to fasten a cap with permanent fastenings, but instead would replace the cap in accordance with prescribed procedures.

The flammable plastic cap of the Pfalzgraff et al. patent, which is permanently fastened in place, is primarily directed for use in ducts which, as a result of their construction, will normally isolate a fire within such ducts for a limited time. Therefore, permitting the ignition of the cap as part of its mode of operation is not usually a serious problem. In a room, however, which may con tain many flammable items, the desirability of using a cap which must burn to open the way to proper sprinkler action is not readily acceptable because of the prospect that a number of flaming caps might initiate more damage than the original fire which is to be controlled. This is true not only of this particular plastic cap but of all prior flammable plastic caps. In addition, it has been found that the plastic used in these caps generally has a higher temperature rating than is a ailable from use of the present invention. Moreover, the plastic is not capable of withstanding extensive periodic wiping because it will score or scratch as a result of the polishing and wiping. Such scratches will change the temperature response characteristics of the head and cap combination, and are therefore, not desirable.

The present invention eliminates these problems in that the cap portion will withstand the numerous Wipings and polishings necessary to maintain cleanliness without affecting its accuracy of response. Moreover, at or above rated temperature the cap portion will be completely removed so as not to obstruct the pattern of the spray emanating from the head. Upon removal by heat there is no cap portion since it has all been melted. Therefore, a new cap assembly will necessarily be placed over the sprinkler thus precluding the possibility of a maintenance man finding an actuated cap and replacing it.

Other advantages of the invention will become apparent by reference to the following description and accompanying drawing which describe and show, for illustrative purposes only, a preferred embodiment of the invention.

In the drawing:

FIG. 1 is a side elevation view, in section, illustrating a typical recessed sprinkler installation with my improved ceiling plate and protective cap combination;

FIG. 2 is a perspective view of the ceiling plate and protective cap combination of FIG. 1 with a portion cut away for clarity of details;

FIG. 3 is an exploded perspective view of the combination of FIG. 2;

Referring now in greater detail to the drawing, 10 indicates a fusible automatic sprinkler recessedly mounted in a ceiling 12 of a room. This mounting is accomplished by threadingly engaging the sprinkler frame 15 into a supply main 16. The sprinkler frame 15 extends through end wall 17 of cuplike casing 18 which may be referred to as the body. This body is threaded as at 19 at its lower outer periphery and extends into an opening 14 in the ceiling.

Each sprinkler is provided with a thermally responsive closure construction and a deflector 21 to disperse the water in a preferred spray pattern. The sprinkler 10 illustrated herein is sold under the name Duraspeed. Other types of sprinklers, however, may be used.

In FIG. 2 the combination of recessed ceiling plate 24 and protective cap 30 are shown joined together by rivets 32 which are integral with the protective cap. These rivets extend perpendicularly to the fiange 36 of the cap and are passed through holes 27 in the flange 26 of plate 24 (see FIG. 3). The plate is preferably formed of sheet metal, but it is conceivable that the objectives of this invention may also be achieved by forming the plate 24 of cast solder. The rivets are preferably spun down or hot formed to form heads 34 which securely hold the flange 26 to the flange 36 of the cap 30.

The protective cap 30 is composed of a fusible solder cast to a uniform thickness with the rivets integral with flange 36. The outer surface of the cap may then be polished to a smooth finish to enhance its appearance and the ease with which it can be wiped clean.

The entire installation is assembled by first placing the body 18 over the frame 15 and threading the body 10 into the main 16. The combination of ceiling plate 24 and cap 30 is then joined to the body by engaging the inward ly turned lip of the plate 24 with the threaded portion 19 of the body and turning the plate and cap until the flanges 2-6 and 36 are screwed firmly into engagement with ceiling 12.

Various solder compositions may be used for the cap, depending on the speed response desired and the ambient temperature expected to be prevalent at the caps.

One composition found to be highly acceptable is a 165 F. solder containing: Bismuth50%; Lead-25%; Cadmium13% and Tin12%.

It is contemplated that for quicker response of the head a 117 F. solder can be used for the cap containing: Bismuth44.7%; Lead-22.6%; Tin-8.3%; Cadmium5.3% and Indium19.1%. This would also permit a greater degree of certainty that the cap would be melted and out of the way of the sprinkler well before the sprinkler is actuated.

At times there may be an oven or other heat generating device used in the room for which a normal tempera ture (e.g. 165 F.) automatic sprinkler head and cap combination would not be desirable because the ambient temperatures about such a device would generally exceed the rated temperature of the normal head and cap. In such a case it will be preferable to use a higher temperature responsive solder for the cap 30 and the fusible element of head 10. For example, to raise the operating rated temperature of the cap 30 and sprinkler 10 it may be desirable to use a solder of Tin-66.7% and Lead 33.33% which has a melting point of 360 F.

Even in the latter application it may be desirable to have the cap of a lower rated solder than the head where speed is of greater interest than the safety factor normally applied for the prevalent ambient temperature. It is conceiva ble that under these circumstances a cap might melt without a sprinkler being set off. This is not to be viewed as a disadvantage in all cases since a replacement ceiling plate 24 and cap 30 combination can easily be screwed into place on threads 19 of the body 18. Rather, this can be viewed as a form of visual safety alarm since it will indicate that the ambient temperature is higher than a desirable level. Moreover, in contrast with a flammable plastic cap, no water damage will occur since no water is released. A flammable plastic cap once ignited by high ambient temperature will set off its sprinkler which could cause unnecessary water damage although no fire exists.

It is further contemplated that occasions may arise where it is desirable to have a lower rated head than the rating of the cap. This would give rise to a quick actuation of the sprinkler shortly after the cap has been melted. This is another approach to deriving quicker response than might be obtained from a cap and sprinkler having the same temperature rating. A natural question which might arise concerns the possibility of the head being actuated prior to the melting of the solder cap. It has been found, however, that the air contained within the cap acts as an insulator which slows the heat transmitted to the head. Therefore, the cap will normally, upon being subjected to the heat of a fire, melt before the sprinkler is actuated. When this occurs, the sprinkler will be, in turn, quickly actuated. A specific arrangement which is demonstrable is a 165 F. solder cap with a 135 F. rated sprinkler for use in areas where ambient temperature normally will not exceed F.

To withstand the rigors of numerous wipings and polishings a cap cast to a uniform thickness of approximately has been found to be durable and amply sensitive to fulfill the advantages set out above.

An additional advantage is fulfilled should the cap be accidentally knocked loose by a maintenance man while wiping the cap. If he were to use permanent fastenings such as sheet metal screws to replace the cap, the cap is still capable of operating effectively if a fire occurs, because the cap will melt away leaving the screws in place and exposing the head without any impediments.

It will be seen from all of the above combinations that the proper sequence of operations under the influence of a fire is a complete removal of the cap 30 and then actuation of head 10 to extinguish a fire.

While the invention has been described in detail it is believed that it essentially comprises a ceiling plate and solder cap combination wherein the cap will melt at a predetermined temperature due to a fire. The sprinkler, normally contained wtihin the cap will thereupon have clear access to properly spray water on the fire in a relatively short time. The above described novel combination thus makes possible the use of sprinklers where they normally would not be used.

The present disclosure has been made by way of example and it is understood that changes in details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as claimed below.

It is intended that such terms of reference as upper, lower, downwardly, etc., in the claim below are intended merely as terms to relate portions of the claimed combination with one another and not as terms of limitation as to the orientation of the combination.

I claim:

1. In a combination comprising:

(I) a ceiling having:

(A) an opening therein, (B) a downwardly presented surface around said opening,

(II) a fire extinguishing sprinkler head assembly which:

(A) has a casing portion located above said surface, (B) has a frame portion extending through said ceiling opening, (C) has a deflector which:

(1) is mounted on said frame portion, (2) is located below said ceiling surface, (III) a ceiling plate which:

(A) has an inner body portion which:

(1) extends through said ceiling opening, (2) adjustably engages said sprinkler casing portion, (B) has an outer flange portion which:

(1) extends from said body portion, (2) overlies said ceiling surface around said opening, (3) has apertures therein,

5 6 (IV) a cap which: References Cited (Agencctzses said sprinkler frame portion and UNITED STATES PATENTS (B) covers said opening, 2,321,755 6/1943 Kost.

the improvements comprising said cap being formed of 5 2 890 758 6/1959 pf fi et a]. solder, said cap having a flange which overlies said ceiling plate flange and is presented to said ceiling surface 3l30790 4/1964 Hodgman 169.40 beyond the outer edge thereof, said cap flange having solder rivet projections integral therewith and lying in M. HENSON WOOD, 111., Primary Examiner.

said ceiling plate flange apertures, and said cap flange 10 having a smooth downwardly presented surface opposite M. Y. MAR, Assistant Examiner. said rivets. 

